package com.twmacinta.util;

import java.io.BufferedInputStream;
import java.io.FileInputStream;
import java.io.FilterInputStream;
import java.io.IOException;
import java.io.InputStream;

/**
 * MD5InputStream, a subclass of FilterInputStream implementing MD5 functionality on a stream.
 * <p>
 * Originally written by Santeri Paavolainen, Helsinki Finland 1996 <br>
 * (c) Santeri Paavolainen, Helsinki Finland 1996 <br>
 * Some changes Copyright (c) 2002 Timothy W Macinta <br>
 * <p>
 * This library is free software; you can redistribute it and/or modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either version 2.1 of the License, or (at your option) any later version.
 * <p>
 * This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Library General Public License for more details.
 * <p>
 * You should have received a copy of the GNU Library General Public License along with this library; if not, write to the Free
 * Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 * <p>
 * See http://www.twmacinta.com/myjava/fast_md5.php for more information on this file.
 * <p>
 * Please note: I (Timothy Macinta) have put this code in the com.twmacinta.util package only because it came without a package. I
 * was not the the original author of the code, although I did optimize it (substantially) and fix some bugs.
 * 
 * @author Santeri Paavolainen &lt;santtu@cs.hut.fi&gt;
 * @author Timothy W Macinta (twm@alum.mit.edu) (added main() method)
 **/

public class MD5InputStream extends FilterInputStream {
	/**
	 * MD5 context
	 */
	private MD5 md5;

	/**
	 * Creates a MD5InputStream
	 * 
	 * @param in
	 *            The input stream
	 */
	public MD5InputStream(InputStream in) {
		super(in);

		md5 = new MD5();
	}

	/**
	 * Read a byte of data.
	 * 
	 * @see java.io.FilterInputStream
	 */
	public int read() throws IOException {
		int c = in.read();

		if (c == -1)
			return -1;

		if ((c & ~0xff) != 0) {
			System.out.println("MD5InputStream.read() got character with (c & ~0xff) != 0)!");
		} else {
			md5.Update(c);
		}

		return c;
	}

	/**
	 * Reads into an array of bytes.
	 * 
	 * @see java.io.FilterInputStream
	 */
	public int read(byte bytes[], int offset, int length) throws IOException {
		int r;

		if ((r = in.read(bytes, offset, length)) == -1)
			return r;

		md5.Update(bytes, offset, r);

		return r;
	}

	/**
	 * Returns array of bytes representing hash of the stream as finalized for the current state.
	 * 
	 * @see MD5#Final
	 */
	public byte[] hash() {
		return md5.Final();
	}

	public MD5 getMD5() {
		return md5;
	}

	/**
	 * This method is here for testing purposes only - do not rely on it being here.
	 **/
	public static void main(String[] arg) {
		try {

			// //////////////////////////////////////////////////////////////
			//
			// usage: java com.twmacinta.util.MD5InputStream [--use-default-md5] [--no-native-lib] filename
			//
			// ///////

			// determine the filename to use and the MD5 impelementation to use

			String filename = arg[arg.length - 1];
			boolean use_default_md5 = false;
			boolean use_native_lib = true;
			for (int i = 0; i < arg.length - 1; i++) {
				if (arg[i].equals("--use-default-md5")) {
					use_default_md5 = true;
				} else if (arg[i].equals("--no-native-lib")) {
					use_native_lib = false;
				}
			}

			// initialize common variables

			byte[] buf = new byte[65536];
			int num_read;

			// Use the default MD5 implementation that comes with Java

			if (use_default_md5) {
				InputStream in = new BufferedInputStream(new FileInputStream(filename));
				java.security.MessageDigest digest = java.security.MessageDigest.getInstance("MD5");
				while ((num_read = in.read(buf)) != -1) {
					digest.update(buf, 0, num_read);
				}
				System.out.println(MD5.asHex(digest.digest()) + "  " + filename);
				in.close();

				// Use the optimized MD5 implementation

			} else {

				// disable the native library search, if requested

				if (!use_native_lib) {
					MD5.initNativeLibrary(true);
				}

				// calculate the checksum

				MD5InputStream in = new MD5InputStream(new BufferedInputStream(new FileInputStream(filename)));
				while ((num_read = in.read(buf)) != -1)
					;
				System.out.println(MD5.asHex(in.hash()) + "  " + filename);
				in.close();
			}
		} catch (Exception e) {
			e.printStackTrace();
		}
	}

}
